Astronomers surveying the outer solar system have revealed that a rare object far beyond Neptune is moving in sync with the eighth planet in an unexpected way. Called 2020 VN40 and first discovered in 2020, it takes 1,655 Earth-years to orbit the sun. The news comes just weeks after 2023 KQ14 — nicknamed “Ammonite” — was found beyond Neptune and Pluto. Together, these newly found objects change the way astronomers think distant objects move and how the solar system evolved.
The orbital path of 2020 VN40 — in yellow — is tilted up and to the left from the orbits of most of ... More
2020 VN40 is currently 140 times farther from the sun than Earth. For context, Neptune is 29 times farther from the sun than Earth. However, the object's orbit is highly elliptical, getting just 40 times farther from the sun than Earth.
Most planets — including Earth — orbit the sun in nearly the same flat plane. Some distant objects, such as 2020 VN40, have orbits that are highly inclined relative to this plane.
The object appears to be in a 10:1 resonance with Neptune, meaning that it orbits the sun once for every ten orbits Neptune completes. It's the first object ever found to do that.
The size of 2020 VN40 is unknown because it's too far away to be directly measured. However, based on its brightness, it may have a diameter of around 56 miles (90 kilometers).
Published this month in the American Astronomical Society’s The Planetary Science Journal, the discovery supports the theory that many distant objects get captured by Neptune’s gravity as they drift through the outer solar system. “This is a big step in understanding the outer solar system,” said Rosemary Pike, lead researcher from the Center for Astrophysics, Harvard and Smithsonian in Cambridge, Massachusetts. “It shows that even very distant regions influenced by Neptune can contain objects, and it gives us new clues about how the solar system evolved.”
It could also shed light on the motion of objects in the outer solar system. “This new motion is like finding a hidden rhythm in a song we thought we knew,” said Ruth Murray-Clay, co-author of the study, from the University of California in Santa Cruz. “It could change how we think about the way distant objects move.”
2020 VN40 took six years to be discovered and for its orbit to be mapped. It was discovered by astronomers working on the Large Inclination Distant Objects survey, a search for unusual objects in the outer solar system with orbits that extend far above and below the plane of the solar system. It’s a region of the solar system that few astronomers have studied. The researchers used the Canada-France-Hawaii Telescope and Gemini North in Hawaii and Magellan Baade and Gemini South in Chile. The LiDO survey has now found over 140 distant objects.
The Vera C. Rubin Observatory in Chile, which published its first stunning images in June, is expected to find many more objects in the outer solar system. “With the imminent start of Rubin Observatory’s Legacy Survey of Space and Time, we expect many more such discoveries to open a new window into the solar system’s past,” said Kathryn Volk of the Planetary Science Institute. Rubin is also expected to find more interstellar objects — such as ancient comet 3I/ATLAS.
Another newly discovered object that could reshape astronomers’ understanding of the solar system’s past is “Ammonite,” or 2023 KQ14, an object discovered in the solar system beyond Neptune and Pluto. Classed as a sednoid — an object similar to Sedna, a dwarf planet candidate in the outer solar system found in 2003 — Ammonite orbits beyond Neptune and has a highly eccentric orbital path. It’s thought to be between 137 and 236 miles (220 and 380 kilometers) in diameter and between 70 and 432 times farther from the sun than Earth.